diametrically different, for the former loves cold water, the latter warm water.

Various provincial writers are now quoted; Mr. Perley, who says that "naturalists now tell us" and "it is now considered settled " that the mackerel is not migratory, but draws off into deep water at the approach of winter, and Mr. Knight and Mr. Fortin, though the reason for these quotations is not apparent, since no reference to the winter habits of the fish can be found therein. He does not refer to the writings of Mr. Ambrose and Mr. Johnson, Canadian writers, who advocate the migratory theory.

Yarrell and Couch are next quoted, though neither of them has ventured to give a decided opinion.

Finally, we have a paragraph compiled from five French encyclope dias, good and bad, no means being afforded of distinguishing the opin ions of Cuvier from those of Chenu's literary staff.

Mr. Whitcher's conclusion is this: that "it is clearly neither necessary nor accurate that mackerel should perform the migrations ascribed to them by American writers."

The migrations of the mackerel are neither proved nor disproved by special pleadings of this description. The spirit of Professor Hind's writings is very different. He writes from the stand-point of an inves tigator, and his book is an important contribution to our knowledge of the habits of fishes in relation to temperature and currents. I feel obliged, however, to call attention to a very serious flaw in his chief argument against the annual migration of the mackerel.

In the chapter on the "Relation of the Supposed Migratory Movements of Mackerel to Isothermal Lines," it is claimed that a migration to the north in the spring "presupposes the movements of bodies of the same great schools of mackerel which are alleged to pass Massachusetts Bay from the waters of the coasts of Virginia and New Jersey, not only through from ten to twelve degrees of latitude, but it assumes that they are able to cross in the early summer, and frequently before spawning, numerous isothermal lines in descending order.”

He then refers to the article upon the Gulf Stream in Petermann's "Mittheilungen" for 1870, in which the marine isothermals for the different months are shown by means of a chart. A table is given showing the isothermals for July. That of 68° would touch the coast at Delaware Bay, that of 630.5 at Long Island, that of 59° at Boston, that of 540.5 at Cape Sable, Nova Scotia, that of 50° at Cape Race, and that of 45°.5 at the Straits of Belle Isle.

From this he concludes that a "a school of fish, moving rapidly from Delaware Bay to the Straits of Belle Isle, would pass in July from a mean temperature of 68° to a mean temperature of 45°, a difference of more than 220 Fahrenheit.

This theory would be very satisfactory if it could be admitted that the

*Hind, op. cit., part ii, pp. 15–17.

isothermals for July indicate the actual temperature of the sea from day to day. In reality the marine isothermals are constantly varying, and, in this respect are different from those printed upon a chart. A glance at the tables in Appendix F, and the conclusions deduced from them in regard to the menhaden (paragraph S5), will show that schools of fish do not find it necessary to force their way through walls of sea temperature, but that their movements from south to north are exactly correlated with the seasonal rise of temperature. As soon as the water at a given point reaches the necessary temperature, which for the mackerel on our own coast appears to be as much as 45°, the fish make their appearance, and with the advance of the season they appear farther and farther to the north. Mackerel do not appear on the coast of Maine until the water is as warm as it was off Cape Hatteras at the time of their first arrival. This is the case whether we suppose their general movement to be parallel with or vertical to the coast line.

I have entered the discussion of this question not with any idea of attempting to prove that mackerel migrate south from the Gulf of St. Lawrence, but to show that a comparatively rapid northward movement in May and June does not necessitate a "sudden plunging from high to low zones of temperature."

Arguments against extended migrations of menhaden.

89. There is no satisfactory evidence that the menhaden pursue extended migrations north and south. The same evidence which tends to show that the shad, salmon, and alewife do not follow this course will will apply, with modifications, to the menhaden.

The menhaden schools at different points along the coast appear to have individual peculiarities, corresponding to those of the shad in the different rivers. A Maine menhaden may easily be distinguished from a Long Island menhaden, a Chesapeake or a Florida one, by certain indescribable characters, easy to perceive but difficult to define. The presence of the crustacean parasite in the mouths of southern menhaden, and its constant absence from those of the north is a very strong argument in favor of local limitation in the range of menhaden schools.

That the same schools of menhaden return year after year to the same feeding grounds is rendered very probable by the statements of Mr. Miles in paragraph 72.

The schools in the southern waters do not receive any apparent increment at the time of desertion of the north coast, nor are the southern waters deserted at the time of abundance in the north. There is, however, a limited north and south migration. The Maine schools on their departure in the fall appear to follow the southward trend of the coast until they strike the hook of Cape Cod, where they are detained for some days; they then round the cape and are again detained by the hook of Montauk Point. They first strike the shore at Point Judith and are

turned over into Peconic Bay by the line of islands stretching across the eastern end of Long Island Sound.

In this same way the Chesapeake schools are said to be detained for some days by the projection of Cape Henry.

The hypothesis of oceanic sojourn of the menhaden.

90. The questions of hibernation and extended migration having been considered, it only remains to discuss the third alternative, that of the possibility of sojourn in the warm strata of the open ocean.

In plate XII is given diagram sections of the North Atlantic Ocean between New York and Bermuda, showing the soundings and isothermal lines obtained in Her Majesty's ship "Challenger", April 24 to May 8, 1873. The vertical scale is necessarily enormously exaggerated, but the diagram shows the presence of strata under the Gulf Stream, and be tween it and the American coast, the temperature of which exactly meets the requirements of the menhaden. At a depth of 50 to 100 fathoms there is a shoreward extension of the warm stratum of 50° to 55° which extends inward one hundred and twenty miles. There are no means of determining the corresponding isothermal lines on the coast of North Carolina, but an extension of much less degree would approach very near the shore in that region. The diagram represents the condition of the sea temperature near New York at the very period when the menhaden are approaching the coast in April, and a similar relation not improbably exists in November, at the time of their departure. The schools of fish swimming out to sea when the shore waters become too cold for them, and driven below the surface by the winds of November, would naturally strike these temperate strata, and being kept from descending deeper by the uniform coldness of the waters below, as well as by the increasing pres sure, and their efforts to approach the shores being also opposed by a tem perature barrier, they would remain in the temperate strata until they were enabled by the warmth of spring to regain their feeding grounds near the shores.

No authorities can be quoted in support of this hypothesis, but, in the case of the menhaden at least, it appears to explain more of the difficult questions in relation to periodical movements than that of hibernation or that of extended migration.

(1.) It presupposes less sudden changes of temperature than that of hibernation. It has been shown that hibernation of fishes is never voluntary, but is a state of torpidity induced like that of æstivation by a change of temperature and surroundings which they have no power to avoid. Before entering upon hibernation or æstivation fishes retreat to the deepest water, and only become completely torpid when they are fol lowed thither by the changed conditions of existence. In the fresh waters of temperate regions fishes do not become entirely torpid in cold weather, but are sufficiently active to be taken with hooks from under the ice. This is also the case in very deep waters in subpolar regions. The

kalleraglitz or American turbot (Reinhardtius hippoglossoides) is taken with hooks, in the dead of winter, under the floe ice of North Greenland at a depth of 300 fathoms; in South Greenland, on the oceanic banks, at C0 and 80 fathoms; and at Fortune Bay, Newfoundland, it is captured in the shore herring-seines at the same season.

So long as the menhaden can avoid the extremes of temperature which they so carefully avoid in the summer by seeking congenial warmth in the ocean strata under the Gulf Stream, need we suppose that they will plunge into the colder strata below?

(2.) It involves less radical changes than hibernation in the habits of the fishes. Some fishes, like the mud-minnow (Umbra limi) of the Eastern United States, are peculiarly adapted for life in the mud; others, such as the "compound breathers" (Labyrinthici) of India, are said to respire with ease with their heads covered by liquid mud. Such fishes, however, are totally different in organization from the free-swimming species of the open seas. All free swimmers are especially heedful to avoid contact with the bottom. This is especially so in the case of the herring family, of which the menhaden is a member. They are provided usually with deciduous scales, and never suffer themselves to come in contact with the bottom. If one of the herring or mackerel tribe is placed in an aquarium, it will be noticed that it keeps itself always free from the bottom. Other fishes in the same tank, such as the sea-bass, tautog, or king-fish, will be seen to rest on the bottom, and even to take refuge under the stones.

It is improbable that mackerel ever voluntarily sink into the mud of the ocean bottom; still more so in the case of the menhaden.

(3.) It accounts better than the other theories for the early appearance of the fish in the spring.

Admitting the possibility of a winter's sojourn in the mud, we are met by a difficulty when we try to account for the prompt appearance of the fishes in the spring. The deeper strata of the ocean are now known to preserve throughout the year the uniform temperature of 220 to 40°. The fish, once mummified in the depths of the ocean, would remain so forever, unless they possess powers unknown to exist in other animals.

On the other hand, if we suppose the fish to be swimming in the strata of mid-ocean, we know that they are in just the position to be susceptible to all the daily variations of temperature. Following, with the advance of the season, the inward curving of the Gulf Stream, the warm strata below it gradually approach the shore. The schools of fish are thus enabled gradually to draw nearer to the coast line, and when the strata of 50° to 55° in temperature touch the coast the menhaden are at hand.

(4.) It explains, as well as the hibernation theory and better than the migration theory, the peculiarity of the schools at different localities along the coast. This was discussed in paragraph 88.

(5.) It explains better than the other theories the appearance of the fish at the time of their arrival in the spring.

The menhaden appear to be bottom feeders. If they migrated coastwise to the south, they would there find feeding-grounds; if they sank to the bottom, they would there find food if they had sufficient vitality to resurrect themselves in the spring; if they passed the winter in the mid-ocean strata, they could obtain no focd and would naturally become emaciated, the accumulated fat of the preceding summer being absorbed.

Rimbaud's classification criticised and a new one proposed.

91. Rimbaud's classification, which is a modification of one recognized in the markets of South France, is very suggestive, but it does not appear to me to be entirely applicable to the fishes of our coast, at least not in the way in which it has usually been adopted.

Rimbaud makes four divisions, viz:

I. Wandering fishes (Poisson nomade).

II. White fishes (Poisson blanc).

III. Bottom fishes (Poisson de roche or Poisson de fond).

IV. Alien or outside fishes (Poisson forain).

The distinction between Classes I and IV does not appear to be very clearly marked. In the Western Atlantic, some of the fishes making up Class IV belong to each of the other classes.

A more natural classification would be in three divisions, which might readily be correlated with the three kinds of migration mentioned in the preceding paragraph.

The first group would include the wandering fishes, the Poisson nomade of Rimbaud, whose migrations are entirely oceanic and coufined to the surface zones. The second group would include the bottom fishes of restricted range, the Poisson de fond of Rimbaud, which move to and from the shore or the shallows, and which do not range. The third group would include the middle classes, those which take advantage of both methods of migration, and corresponds approximately to Rimbaud's second division. "White fishes" seems hardly an appropri ate name: "coast fishes" would perhaps be more expressive.

Colonel Lyman, in his report "On the Limits of Artificial Culture, and the Possible Exhaustion of Sea-fisheries" (p. 67), speaks of the first class as "the wandering or schooling fishes of the high seas." The term "schooling" is liable to mislead, for the "white fishes" also school. Among the wandering fishes he mentions only "the herring (Clupea elongata), mackerel (Scomber vernalis), menhaden (Alosa menhaden), cod (Gadus morrhua)," &c. The cod and herring most certainly are "white fishes," and the menhaden and mackerel are certainly not to be ranked with "those which appear on the coast only when 'migrating,' and then in vast but uncertain troops" (p. 63).

*

Report of the Commissioners of Fisheries (of Massachusetts) for the year ending January 1, 1870, pp. 58-67.